Okay, last week, I needed to recreate my WordPress network of sites, complete with Donncha’s domain mapping plugin. I got a little hung up on getting it working, as it has been over six months since I set up the first time, but there is now plenty of documentation online for the mildly experienced WordPress user to follow and get their own network up and running.
First, you need to install WordPress 3.0.4 and get it running. Then follow this document to the letter, which will set up your network of sites: http://codex.wordpress.org/Create_A_Network.
It is very important that you set up a SUBDOMAIN network install and NOT a SUBDIRECTORY network install!
Next step is to install Donncha’s domain mapping plugin. The current version of the plugin is 0.5.3. Otto has an excellent post detailing the steps required to map the subdomains to the actual domain names you wish to use. You can view Otto’s post at http://ottopress.com/2010/wordpress-3-0-multisite-domain-mapping-tutorial/
I had a little trouble getting the domain mapping going the first time, and posted this thread back in June: http://wordpress.org/support/topic/multiple-multisite-installs-on-single-ip. With many thanks to Andrea_r and Ipstenu, I was able to configure Apache and get my domain mapped network up and running.
You can also mix domains and subdomains on a single network multisite domain mapped installation; i.e. example123.com, example456.com, and blog.example789.com. Check out this thread on how to accomplish this task: http://wordpress.org/support/topic/30-multisite-domain-mapping-and-subdomains
Once again, many, many thanks to Donncha, Andrea_r, Otto, and Ipstenu! Please feel free to comment and add anything which I may have left out.